Stamping tool, casting mold and methods for structuring a surface of a work piece

ABSTRACT

A mold or stamping tool with which a simple, cost-effective stamping or molding in the nanometer range is enabled by a molding or stamping surface layer of the mold or tool being provided with hollow chambers formed by anodic oxidation.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a division of co-pending U.S. patentapplication Ser. No. 10/281,376.

BACKGROUND OF THE INVENTION

[0002] Field of the Invention

[0003] The present invention relates to a stamping tool having astructured stamping surface, a casting mold, a method for producing astamping tool or a casting mold having a structured stamping surface,and methods for structuring a surface of a workpiece.

[0004] Stamping constitutes a non-cutting manufacturing method forproducing a relief-like or structured surface on a workpiece. A stampingtool with a profiled or structured stamping surface is used for this.The stamping surface is pressed with such a stamping force onto thesurface to be structured of the workpiece or rolled on this, so that theworkpiece becomes plastic and flows into depressions in the stampingtool or the stamping surface. Due to the considerable stamping forcesemployed, the stamping tool and the stamping surface are usually made ofmetal.

[0005] Further, molding is known. A casting mold with a structuredmolding face can be used for producing a cast workpiece with astructured surface by casting.

[0006] In the present invention nanometer range is understood to meanprofiling or structuring with structural widths <1000 nm, especially<500 nm. The structural width designates the dimension by whichindividual structural elements, such as bumps, are repeated, that is,for example the average distance of adjacent bumps from one another orof depressions from one another.

[0007] 2. Description of Related Art

[0008] It is very expensive to manufacture a stamping tool with a veryfinely structured or profiled stamping surface. To create a so-called“moth eye structure”—evenly arranged, egg carton-like bumps—or finegrooves in the nanometer range, it is known from practice to use alighting pattern with periodic intensity modulation for illuminatingphoto-sensitive material via two interfering laser beams. After theilluminated material develops, a periodic surface structure results,which is molded into other materials using various replication methodsand finally into nickel, for example, by electroforming. This type ofmanufacturing is very expensive and is suited only for structuring evensurfaces.

[0009] In the nanometer range lithographic methods for structuring astamping surface of a stamping tool can still only be used in a limitedway. It should be noted here that the wavelength of the visible lightalone is already 400 to 750 nm. In each case lithographic methods arevery costly.

[0010] German Patent DE 197 27 132 C2 discloses the manufacturing of astamping tool by means of electrolytic machining. During electrolyticmachining a metallic stamping surface of the stamping tool is treatedelectrolytically, wherein, being an anode in a fast-flowing electrolyte,the metal of the stamping surface is located at a minimal distanceopposite a cathode and is dissolved in surface terms. The metal or thestamping surface contains the structure determined by the form of thecathode, and the cathode thus forms a recipient vessel that is shapedelectrochemically. DE 197 27 132 C2 also provides the use of acylindrical rotation electrode, whose covering surface presents anegative form of the desired stamping structure. Here, too, there isconsiderable expense involved and structuring in the nanometer range isat least only partly possible.

[0011] The use of anodically oxidised surface layers made of aluminiumor magnesium in casting molds to increase resistance is known from SwissPatent CH 251 451. However, the forming of hollow chambers by oxidationfor structuring a molded article in the nanometer range is notdisclosed.

[0012] Forming hollow chambers with anodic oxidation of aluminium isdescribed in published European Patent Application EP 0 931 859 A1, forexample.

[0013] However, the related art does not provide a cost-effectivesolution to produce a workpiece, like a stamped piece, or casting with asurface structered in the nanometer range.

[0014] Consequently, there is a need for a stamping tool, a castingmold, a method for manufacturing a stamping tool or a casting mold, amethod for structuring a surface of a workpiece and a method for using asurface layer provided with open hollow chambers, wherein structuring inthe nanometer range is enabled in a simple and cost-effective manner.

SUMMARY OF INVENTION

[0015] Object of the present invention is to provide a stamping tool, acasting mold, a method for manufacturing a stamping tool or a castingmold, a method for structuring a surface of a workpiece and a method forusing a surface layer provided with open hollow chambers, whereinstructuring in the nanometer range is enabled in a simple andcost-effective manner.

[0016] One aspect of the present invention is to use a porous oxidelayer and especially a surface layer, formed via anodic oxidation andprovided with open hollow chambers, as stamping surface of a stampingtool. This leads to several advantages.

[0017] First, an oxide layer, especially the preferably providedaluminium oxide, is relatively hard. With respect to the often very highstamping forces this is an advantage for being able to stamp workpiecesof various materials and for achieving a long tool life of the stampingtool.

[0018] Second, model-free oxidation is very easy and cost-effective tocarry out. In particular, producing hollow chambers is (quasi)independent of the form and configuration of the cathodes employed, so amodel or negative form is not required, as in electrolytic machining.

[0019] Third, the provided model-free forming of open hollow chambersvia anodic oxidation enables structures to be manufactured in thenanometer range very easily and cost-effectively. In particular,structural widths of 500 nm and less, even 100 nm and less are possible.

[0020] Fourth, depending on choice of procedural conditions theconfiguration—regular or irregular—and the surface density of the hollowchambers can be varied as required.

[0021] Fifth, by likewise simply varying the proceduralconditions—especially by variation of the voltage during anodising—theform of the hollow chambers and thus the structure of the stampingsurface can be adjusted and varied.

[0022] Sixth, the anodically oxidised surface layer can be useddirectly, thus without further molding, as the stamping surface of astamping tool.

[0023] A further aspect of the present invention is to use a porousoxide layer and especially a surface layer with open hollow chambers,formed by anodic oxidation directly or model-free, thus independent of acathode form, as molding face or inner face of a casting mold. This hasa number of advantages.

[0024] First, an oxide layer, especially the preferably providedaluminium oxide, is relatively hard. With respect to the often very highforces utilised in casting or molding this is an advantage for beingable to produce workpieces of various materials and for achieving a longshelf life of the casting mold.

[0025] Second, the model-free oxidation is very easy and cost-effectiveto carry out. Producing hollow chambers is (quasi) independent on theform and configuration of the cathodes used, and a model or negativeform is therefore not required.

[0026] Third, the model-free forming of open hollow chambers as providedvia anodic oxidation enables structures to be manufactured in thenanometer range very easily and cost-effectively. In particular,structural widths of 500 nm and less, even 100 nm and less are possible.

[0027] Fourth, depending on choice of procedural conditions theconfiguration—regular or irregular—and the surface density of the hollowchambers can be varied as required.

[0028] Fifth, by likewise simply varying the proceduralconditions—especially by variation of the voltage during anodising—theform of the hollow chambers and thus the structure of the surface can beadjusted and varied.

[0029] Sixth, the anodically oxidised surface layer can be useddirectly, thus without further molding, as the surface of a castingmold.

[0030] Further advantages, properties, features and goals of the presentinvention will emerge from the following description of preferredembodiments with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 shows a very schematic sectional elevation of a proposedstamping tool and a workpiece structured therewith according to a firstembodiment; and

[0032]FIG. 2 shows a very schematic sectional elevation of a proposedcasting mold and a workpiece structured therewith according to an secondembodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0033] In a highly simplified sectional elevation, FIG. 1 shows aproposed stamping tool 1 with a structured, i.e. profiled or relief-likestamping surface 2. The stamping surface 2 is formed by a flat side of asurface layer 3, which is provided with open hollow chambers 4 producedby anodic oxidation.

[0034] In the illustrative example, the surface layer is applied to asupport 5 of the stamping tool 1. For example, the surface layer 3 isapplied to the support 5 by plasma coating. But the surface layer 3 canalso be formed directly by the support 5, and thus be a surface area ofthe support 5.

[0035] It is understood that the surface layer 3 can also be depositedon the support 5 using other methods.

[0036] In the illustrative example the surface layer 3 preferablyconsists of aluminium which is applied to the support 5 especially viaplasma coating and adheres well to the support 5 preferably made ofmetal, especially iron or steel.

[0037] The surface layer 3 is oxidised anodically at least partially inthe illustrative example to the depth of a covering layer 6, whereby thehollow chambers 4 are formed in the surface layer 3. The hollow chambers4 are formed immediately and/or without any model or pattern, i.e. thearrangement, distribution, form and the like of the hollow chambers 4—asopposed to electrolytic machining—is, thus, at least essentiallyindependent of the surface shape and the proximity of the cathode (notshown) used in oxidation. Moreover, according to the invention, the“valve effect”, namely the occurring, independent formation of hollowchambers 4 during oxidation or anodisation of the surface layer 3,—atleast in particular in the so-called valve metals—is used. Thisimmediate or undefined formation of the hollow chambers 4 does notpreclude an additional (before or after) formation or structuring of thestamping surface 2 or the hollow chambers 4 by means of a negative form.

[0038] Depending on how completely or how deeply the surface layer 3 isoxidised, or whether the surface layer 3 is formed directly by thesupport 5, the surface layer 3 can correspond to the oxidised coveringlayer 6. In this case, for example, the intermediate layer 7, which iscomprised of aluminium in the illustrative example and which promotesvery good adhesion between the covering layer 6 and the support 5, canbe omitted.

[0039] For example, according to an alternative embodiment, the uncoatedsupport 5 can be oxidised anodically on its surface forming the stampingsurface 2 by formation of a porous oxide layer or hollow chambers 4.This is possible for example for a support 5 made of iron or steel,especially stainless steel. In this case the surface layer 3 thencorresponds to the covering layer 6, i.e. the oxidised layer.

[0040] Aluminium and iron or steel, especially stainless steel, havealready been named as particularly preferred material, used at leastsubstantially for forming the anodically oxidised surface layer 3 or thecovering layer 6. However, silicon and titanium as well as other valvemetals for example can also be used.

[0041] In the illustrative example the proportions in size are notpresented true to scale.

[0042] The stamping tool 1 or its stamping surface 2 preferably has astructural width S in the nanometer range, especially from 30 to 600 nmand preferably from 50 to 200 nm.

[0043] The hollow chambers 4 or their openings have an average diameterD of essentially 10 to 500 nm, preferably 15 to 200 nm and especially 20to 100 nm.

[0044] In the illustrative example the hollow chambers 4 are designedessentially lengthwise, wherein their depth T is preferably at leastapproximately 0.5 times the above-mentioned, average diameter D andespecially approximately 1.0 to 10 times the diameter D.

[0045] The hollow chambers 4 are designed here at least substantiallysimilarly in shape. In particular, the hollow chambers 4 are designedsubstantially cylindrically. But the hollow chambers 4 can also presenta form deviating therefrom, for example they can be designedsubstantially conically.

[0046] In general, the hollow chambers 4 can also have a cross-sectionvarying in its depth T in form and/or diameter. In addition to this, thehollow chambers 4 can be designed substantially conically as a roughstructure for example, and provided along their walls with many finedepressions (small hollow chambers) to form a fine structure in eachcase.

[0047] The hollow chambers 4 are preferably distributed at leastsubstantially uniformly over the surface of the surface layer 3 or overthe stamping surface 2. However, uneven distribution is also feasible.

[0048] The hollow chambers or their openings are preferably distributedover the stamping surface 2 with a surface density of 10⁹ to 10¹¹/cm².In the illustrative example the surface density is substantiallyconstant over the stamping surface 2. But the surface density can alsovary partially on the stamping surface 2 as required.

[0049] The area of the openings of the hollow chambers 4 is, at themost, preferably 50% of the extension area of the stamping surface 2. Asufficiently high stability or carrying capacity of the stamping surface2 or the surface layer 3/covering layer 6 is hereby achieved withrespect to the high stresses arising during the stamping.

[0050] In general, the form, configuration, surface density and the likeof the hollow chambers 4 can be controlled by corresponding choice ofthe procedural conditions during anodic oxidation. For example, withoxidation of aluminium under potentiostatic conditions—with at leastsubstantially constant voltage—an at least substantially evencross-section of the hollow chambers 4 is achieved over their depth T,i.e. an at least substantially cylindrical form. Accordingly, the formof the hollow chambers 4 can be influenced by varying the voltage. Forexample, galvanostatic oxidation—i.e. at an at least substantiallyconstant current—leads to a somewhat conical or hill-like form of thehollow chambers 4, so that a type of “moth eye structure” or the likecan be formed in this way. The surface density of the hollow chambers 4,i.e., the number of hollow chambers 4 per surface unit the stampingsurface 2, depends inter alia on the voltage and the current duringanodising.

[0051] As required, the hollow chambers 4 can vary in their form, depthand/or surface density over the stamping surface 2, especiallypartially, and/or be designed only partly on the stamping surface 2.

[0052] And, if required, the stamping surface 2 can also be modifiedbefore and/or after oxidation—creation of the hollow chambers 4—forexample via a lithographic process, etching and/or other, preferablymaterial-stripping methods, for example to create a rough structure inthe form of paths, ridges, areas with or without hollow chambers 4,large-surface bumps or depressions and the like on the stamping surface2.

[0053] Chemical sizing, especially by partial etching of oxide material,can also be carried out to modify the stamping surface 2 or the hollowchambers 4. In this way the surface ratio of the opening surfaces of thehollow chambers 4 to the extension area of the stamping surface 2 can bevaried or increased. It is understood that other modifications of thestamping surface 2 or of the hollow chambers 4 can also be made,depending on reaction time and intensity.

[0054] A particular advantage of the proposed solution is that thestamping surface 2 can also be designed in a curved manner—for examplecylindrically—or bulged—for example lenticular or hemispherical. Inparticular the stamping surface 2 can have practically any shape at all.Compared to the prior art it is thus not necessary that the stampingsurface 2 or the surface of the surface layer 3/covering layer 6 is atleast substantially even.

[0055] The figure also shows a workpiece 8, likewise in a highlysimplified, not true-to-scale sectional diagram, in the already stampedstate, i.e. with a surface 9 already structured by the stamping tool 1.Stamping takes places especially by the stamping tool 1 being pressedwith a corresponding stamping force onto the surface 9 of the workpiece8 to be structured, so that the material of the workpiece 8 flows atleast partially into the hollow chambers 4. Here it is not necessarythat the workpiece 8, as illustrated diagrammatically in the figure, isdesigned in a monoblock manner. Instead, the workpiece 8 can alsopresent another type of surface layer or surface coating or the like,not illustrated here, which forms the surface 9 and is structured ordesigned in a relief-like manner by means of the stamping tool 1.

[0056] Instead of the stamp-like embossing the stamping tool 1 can beunrolled with corresponding shaping/form of the stamping surface 2and/or the surface 9 to be structured. By way of example the stampingsurface 2 and/or the surface 9 to be structured can be designed in acurved manner—for example cylindrically—or in a bulged manner to enablereciprocal unrolling for structuring the surface 9.

[0057] Both a die stamping process and also a rolling stamp process canbe realized with the proposed solution.

[0058] Furthermore, the proposed solution can be used for embossing aswell as closed-die coining or coining. A corresponding abutment for theworkpiece 8 or a corresponding countertool is not illustrated forclarification purposes.

[0059] The proposed stamping tool 1 allows very fine structuring of theworkpiece 8 or its surface 9. If needed the workpiece 8 or the surface 9can also be profiled or structured repeatedly, first with a roughstructured stamping tool—optionally manufactured also in customaryfashion—and then with the finer structured proposed stamping tool 1. Alower stamping force is employed, especially during the second stampingprocedure using the finer stamping tool 1 and/or, in an intermediatestep, the surface 9 is hardened in order not to fully neutralise therough structure produced at first stamping, but to achieve superpositionfrom the rough structure and the fine structure of both stamping tools.Thus, it is possible, for example, to create on the surface 9 relativelylarge bumps of the order of 0.1 to 50 μm each with several, relativelysmall protrusions, for example of the order of 10 to 400 nm, on thesurface 9 of the workpiece 8.

[0060] The proposed solution very easily and cost-effectively enablesvery fine structuring of the surface 9. Accordingly, there is a verybroad area of application. For example, such especially very finestructuring can be utilised in anti-reflex layers, for alteringradiation emission of structured surfaces, in sensory analysis, incatalysis, in self-cleaning surfaces, in improving surface wetabilityand the like. In particular, the proposed solution also extends to theuse of workpieces 8 with structured surfaces 9 that have been structuredby use of the proposed stamping tool 1 for the purposes mentionedhereinabove.

[0061] In particular the proposed solution is suited for stampingsynthetic materials—for example PMMA (polymethyl methacrylates), Teflonor the like, metals—for example gold, silver, platinum, lead, idium,cadmium, zinc or the like, polymer coatings—for example paints, dyes orthe like, and inorganic coating systems etc.

[0062] Expressed in general terms, an essential aspect of the presentinvention according to the first embodiment is using a surface layerwith hollow chambers formed by anodic oxidation as bottom die or upperdie, to enable surface structuring in the nanometer range.

[0063] Now, the second embodiment of the present invention is discussedwith reference to FIG. 2.

[0064] In a highly simplified partial sectional elevation, FIG. 2 showsa proposed casting mold 11 with an at least partially structured, thusprofiled or relief-like inner face or molding face 12. The face 12 isformed by a top or flat side of a surface layer 13 that is provided withopen hollow chambers 14 produced by anodic oxidation.

[0065] In the illustrative example, the surface layer 13 is applied to asupport 15 of the casting mold 11. For example, the surface layer 13 isapplied to the support 15 by plasma coating. But the surface layer 13can also be formed directly by the support 15, and thus be a surfacearea of the support 15.

[0066] It is understood that the surface layer 13 can also be depositedon the support 15 using other methods.

[0067] In the illustrative example, the surface layer 13 preferablycomprises aluminium, which is applied to the support 15 especially viaplasma coating and adheres well to the support 15 preferably made ofmetal, especially iron or steel.

[0068] The surface layer 13 is oxidised anodically at least partially,in the illustrative example to the depth of a covering layer 16, bymeans of which the hollow chambers 14 are formed in the surface layer 13or covering layer 16. The hollow chambers 14 are formed directly ormodel-free, that is, the configuration, distribution, form and the likeof the hollow chambers 14 is, compared to electrolytic machining,therefore at least substantially dependent on the surface shape andproximity of the cathodes (not illustrated here) used during oxidation.Rather, the ‘valve effect’ is made use of here, as per the invention,namely the automatic development of the hollow chambers 14 occurringduring oxidation or anodising of the surface layer 13, at leastespecially with so-called valve metals. Such direct and model-freeproduction of the hollow chambers 14 does not exclude additional (prioror subsequent) forming or structuring of the face 12 or of the hollowchambers 14

[0069]

completely or how deeply the surface layer 13 is oxidised, or whetherthe surface layer 13 is formed directly by the support 15, the surfacelayer 13 can correspond to the oxidised covering layer 16. In theillustrative example in this case, for example, the intermediate layer17, which is comprised of aluminium and which promotes very goodadhesion between the covering layer 16 and the support 15, can beomitted.

[0070] For example, according to a design alternative the uncoatedsupport 15 can be oxidised anodically on its surface forming the face 12by formation of a porous oxide layer or hollow chambers 14. This ispossible for example for a support 15 made of iron or steel, especiallystainless steel. In this case the surface layer 13 then corresponds tothe covering layer 16, i.e., the oxidised layer.

[0071] Aluminium and iron or steel, especially stainless steel, havealready been named as particularly preferred material, used at leastsubstantially for forming the anodically oxidised surface layer 13 orthe covering layer 16. However, silicon and titanium as well as othervalve metals for example can also be used.

[0072] In the illustrative example the proportions in size are notpresented true to scale.

[0073] The face 12 preferably has a structural width S in the nanometerrange, especially of 130 to 600 nm and preferably of 50 to 200 nm.

[0074] The hollow chambers 14 or their openings have an average diameterD of essentially 10 to 500 nm, preferably 15 to 200 nm and especially 20to 100 nm.

[0075] In the illustrative example, the hollow chambers 14 are designedessentially lengthwise, wherein their depth T is preferably at leastapproximately 0.5 times the above-mentioned, average diameter D andespecially approximately 1.0 to 10 times the diameter D.

[0076] The hollow chambers 14 are designed here at least substantiallyidentically. In particular the hollow chambers 14 are designedsubstantially cylindrically. But the hollow chambers 14 can also presenta form deviating therefrom, for example they can be designedsubstantially conically.

[0077] In general the hollow chambers 14 can also have a cross-sectionvarying in its depth T in form and/or diameter. In addition to this, thehollow chambers 14 can be designed substantially conically as a roughstructure for example, and provided along their walls with many finedepressions (small hollow chambers) to form a fine structure in eachcase.

[0078] The hollow chambers 14 are preferably distributed at leastsubstantially uniformly over the surface of the surface layer 13 or overthe face 12. However, uneven distribution is also feasible.

[0079] The hollow chambers or their openings are preferably distributedwith a surface density of 10⁹ to 10¹¹/cm. In the illustrative examplethe surface density is substantially constant over the face 12. But thesurface density can also vary selectively on the surface 12 as required.

[0080] The area of the openings of the hollow chambers 14 is at the mostpreferably 50% of the extension area of the face 12. A sufficiently highstability or carrying capacity of the face 12 or the surface layer13/covering layer 16 is hereby achieved with respect to the highstresses arising partially from molding or casting.

[0081] In general the form, configuration, surface density and the likeof the hollow chambers 14 can be controlled by corresponding choice ofthe procedural conditions during anodic oxidation. For example, withoxidation of aluminium under potentiostatic conditions—i.e., at at leasta substantially constant voltage—an at least substantially uniformcross-section of the hollow chambers 14 is achieved over their depth T,i.e., an at least substantially cylindrical form. Accordingly, the formof the hollow chambers 14 can be influenced by varying the voltage. Forexample, galvanostatic oxidation, i.e. at an at least substantiallyconstant current, leads to a somewhat conical or hill-like form of thehollow chambers 14, so that a type of “moth eye structure” or the likecan be formed in this way. The area density of the hollow chambers 14,i.e., the number of hollow chambers 14 per area unit on the face 2,depends inter alia on the voltage and the current during anodising.

[0082] As required, the hollow chambers 14 can vary in their form, depthand/or surface density over the face 2, especially partially, and/or bedesigned only partially on the face 12.

[0083] And, if required, the face 12 can also be modified before and/orafter oxidation—thus creation of the hollow chambers 14—for example, viaa lithographic process, etching and/or other, preferablymaterial-stripping methods, for example to create a rough structure inthe form of paths, ridges, areas with or without hollow chambers 14,large-surface bumps or depressions and the like on the face 12.

[0084] Mechanical processing and/or chemical sizing, especially bypartial etching of oxide material, can also be carried out to modify theface 12 or the hollow chambers 14. In this way, the area ratio of theopening areas of the hollow chambers 14 to the extension area of theface 12 can be varied or increased. It is understood that othermodifications of the face 12 or of the hollow chambers 14 can also bemade, depending on reaction time and intensity.

[0085] A particular advantage of the proposed solution is that the face12 can also be designed in practically any shape at all.

[0086] The figure also shows a molded article or workpiece 18, likewisein a highly simplified, not true-to-scale, sectional diagram, in thealready finished state, i.e., with a surface 19 already structured bythe casting mold 11 after casting.

[0087] The proposed casting mold 11 allows very fine structuring of theworkpiece 18 or its surface 19. It is possible, for example, to createrelatively large bumps of the order of 0.1 to 50 μm each with several,relatively small projections on the surface 19, for example of the orderof 10 to 400 nm, on the surface 19 of the workpiece 18.

[0088] The proposed solution very easily and cost-effectively enablesvery fine structuring of the surface 19. Accordingly, there is a verybroad area of application. For example, such especially very finestructuring can be utilised in anti-reflex layers, for alteringradiation emission of structured surfaces, in sensory analysis, incatalysis, in self-cleaning surfaces, in improving surface wettabilityand the like.

[0089] Expressed in general terms, an essential aspect of the presentinvention is casting or molding a surface layer with hollow chambersformed directly or model-free by anodic oxidation, to enable surfacestructuring in the nanometer range.

[0090] The present invention is especially not limited to a casting mold11 in the narrower sense. Rather, the surface layer 13 or covering layer16 is to be understood as model for a general structuring of a surface,a tool, a workpiece or the like in the nanometer range. In particular,the model may be molded in any way at all. And in particular, noreshaping is required when molding. For example, with the workpiece 18to be manufactured having a structured surface 19, this can be a castarticle, wherein the surface 19 is structured by casting or decanting orany molding of the mold 11.

[0091] In general, the present invention enables a simple,cost-effective stamping or molding in the nanometer range by a surfacelayer with hollow chambers formed by anodic oxidation being used asmatrix or as casting mold.

[0092] Technical Applicability

[0093] The proposed solution very easily and cost-effectively enablesvery fine structuring of the surface. Accordingly, there is a very broadarea of application. For example, such especially very fine structuringcan be utilised in anti-reflex layers, for altering radiation emissionof structured surfaces, in sensory analysis, in catalysis, inself-cleaning surfaces, in improving surface wetability and the like. Inparticular, the proposed solution also extends to the use of workpieceswith structured surfaces that have been structured by use of theproposed stamping tool for the purposes mentioned hereinabove. Further,the proposed solution can be used for casting with practically anymaterial, since aluminium oxide especially is highly resistantmechanically, thermally and/or chemically.

What is claimed is:
 1. Stamping tool with a structured stamping surface,wherein the stamping surface is formed by an anodically oxidised surfacelayer or covering layer with open hollow chambers created model-free bythe anodic oxidation, wherein the stamping surface is structured atleast partially in the nanometer range by the hollow chambers. 2.Stamping tool according to claim 1, wherein the structural width of thestamping surface is 30 to 600 nm.
 3. Stamping tool according to claim 1,wherein the hollow chambers have opening areas with an average diameterof 10 to 500 nm
 4. Stamping tool according to claim 1, wherein thehollow chambers have opening areas with an average, at least essentiallyuniform diameter of 15 to 200 nm.
 5. Stamping tool according to claim 1,wherein the hollow chambers have a depth, which greater than the averagediameter of the hollow chambers.
 6. Stamping tool according to claim 1,wherein the hollow chambers are conically shaped.
 7. Stamping toolaccording to claim 1, wherein the hollow chambers vary at least in oneof form, depth, and surface density.
 8. Stamping tool according to claim1, wherein the stamping surface comprises both a fine and roughstructure.
 9. Stamping tool according to claim 1, wherein the stampingsurface is curved.
 10. Stamping tool according to claim 1, wherein thesurface layer or the covering layer with the hollow chambers is formedat least substantially of a material from the group consisting ofaluminium oxide, silicon oxide, iron oxide, oxidised steel and titaniumoxide.
 11. Mold with a molding face formed of an anodally oxidizedsurface or covering layer with open hollow chambers created model-freeby the anodic oxidation, wherein the molding face has a structure formedat least partially by the hollow chambers which have diameters in ananometer range.
 12. Mold according to claim I 1, wherein the structuralwidth of the molding face is essentially 30 to 600 nm.
 13. Moldaccording to claim I 1, wherein the hollow chambers have opening areaswith an average diameter of 10 to 500 nm.
 14. Mold according to claim11, wherein the hollow chambers have opening areas with an average, atleast essentially uniform diameter of 15 to 200 nm.
 15. Mold accordingto claim 11, wherein the hollow chambers have a depth, which greaterthan the average diameter of the hollow chambers.
 16. Mold according toclaim 11, wherein the hollow chambers are designed conically.
 17. Moldaccording to claim 11, wherein the hollow chambers vary at least in oneof form, depth, and surface density.
 18. Mold according to claim 11,wherein the molding face surface comprises both a fine and roughstructure.
 19. Mold according to claim 11, wherein the surface layer orthe covering layer with the hollow chambers is formed at leastsubstantially of a material from the group consisting of aluminiumoxide, silicon oxide, iron oxide, oxidised steel and titanium oxide.